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发表于 2008-07-15 14:06
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回复: 谁有这套箱子的详细资料...(21HIFI不详细)
KEF Maidstone R109
by Chris BinnsIssue 3 - November 1999There cannot be many people with even a mild interest in hi-fi to whom the initials KEF mean nothing. From budget systems to esoterica, the company has held a high profile in the market place for many years. I should imagine that even if you have never actually owned a pair of KEF loud-speakers you could probably name at least one model, utter all, you have nearly forty years worth of product to choose from. Founded in 1961 by the now legendary Raymond Cooke, KEF (short for Kent Engineering and Foundry) quickly established an innovative approach to loudspeaker design that would keep them in the limelight for years to come. Their approach was novel in so much as they were one of the first companies to use synthetic materials in the cone assemblies of their drive units: Polystyrene and melinex being two early examples. One of the first products to emerge from this development work with these materials was the now legendary B139 bass unit. Due to the companies policy of making their units available to other manufacturers this radical design became something of au acoustic icon - if a loudspeaker design used one of these you knew that it was serious about low frequencies.
Several years later, in collaboration with the BBC, Cooke developed the drive units that would be pivotal in the design of the highly successful and influential LS3/5A, the B110 and T27.
These groundbreaking units incorporated materials such as Bextrene and Neoprene, the characteristics of which displayed several advantages over conventional paper based diaphragms. The new devices were superior in stability over a considerably wider range of both temperature and humidity. They exhibited low coloration and were suitable for mass production to a consistent standard within close tolerances. These developments changed the course of loudspeakers for the next decade or so and provided the basic template for numerous uncoloured designs throughout the seventies.
When you bear in mind that at a conservative estimate, the B110 and T27 units found their way into some three million speakers world-wide, I think it is entirely fair to say that, on this evidence alone, KEF have been something of a major influence in audio. The KEF company's auspicious first years were followed by a whole series of innovations. The sixties saw another first in their incorporation of computer technology in designing both cabinets and drive units. KEF were also the first company to use separate enclosures for each drive unit, as exhibited in the Reference 105's which were first produced in the late seventies. The eighties saw the introduction of the coupled cavity bass loading system which gave more control over drive units at frequency extremes. More recently in the early nineties, they introduced the Uni-Q driver. Not always without a degree of controversy these ideas have helped and sometimes shaped the art of loudspeaker design in the last three decades.
To the best of my recollection I have owned three different KEF loudspeakers. At least one pair (104aBs) are remembered with both affection and admiration for surviving the rigorous and unreasonable demands of student life, whilst maintaining a degree of dignity regardless of the sometimes questionable material fed to them. Post college, in the environs of the recording studio, I remember being absolutely floored by the awesome power of the KM-1 active studio monitors. Their enormous cabinets each boasted no less than four 15" bass units and a total of 1.6 Kilowatts of amplification. When a company with a track record such as KEFs decides to launch a flagship i.e. the culmination of everything that they know about loudspeaker design, the very least we should do is sit up and take notice.
Development of the Maidstone began in the Autumn of 1995. KEF had already established some reasonably large and well regarded designs, such as the Reference four, but the company had produced nothing suitable for the world arena of high end heavyweight loudspeaker design. By contrast, container loads of large, esoteric loudspeakers were being shipped from the United States. To successfully compete in this market KEF needed to produce a loudspeaker to satisfy an extremely demanding list of criteria. The new unit would have to have a massive dynamic range, wide band width, low coloration, good imaging and overall musical quality plus the capability to deliver high (read realistic) volume levels, with minimum compression and distortion, in a large room. The design team could take some consolation from the fact that physical size and budget constraints did not appear to be too severe. Confronted with this challenge the engineers decided to start with a clean slate. It was not a case of pressing into service existing components designed for other systems. Every part of the Maidstone was drawn up with the final product in mind. Strangely enough, the design solution exhibits a return to more traditional values. With the exception of the Uni-Q, it appears that KEF has omitted many of the other innovations for which it is famous.
The Maidstone, once fully assembled, is large and very heavy. Each of the speakers arrives in two sections, and even in this state it takes two people and a lot of sweat to unpack, move and install them. If you don't believe me yet, maybe you will when I tell you that the complete cabinet is approximately 4ft high by 2ft wide with similar depth and weighs in at around 200lbs, or nearly 90Kgs. The weak hearted or spinally impaired should take notice of these facts and approach installation with some caution.
Each assembled cabinet comprises a bass bin, an upper bass cabinet and the mid I top box. The substantially braced bass bin has an internal volume of a 145 litres and is reflex loaded by two ports, each 100mm diameter and 420mm long, flared to avoid turbulence. KEF supplied a spare bass drive unit - not I might add because there was any likelihood of one failing but because they are proud of it. And so they should be. This is not just another 15" bass unit; it is one of the most beautifully engineered devices I have ever seen. Technically it is something of a masterpiece, incorporating a short (10mm) voice coil immersed in a long magnetic gap. This provides lower distortion and greater stability than the more conventional motor structure which utilises a long coil and short gap. The adopted approach is a lot more expensive to produce, primarily due to the cost of engineering the massive magnet assembly needed to generate and focus the flux evenly. The cone is a slightly flared, bonded pulp structure, terminated in a synthetic rubber suspension and complimented by a double rear spider assembly again aiding stability. This unit covers the bottom end of the frequency spectrum up to about 100Hz.
The two upper sections of the cabinet sit on the bass cabinet, coupled to it by 3 gold plated cup and cone assemblies. The lower of these contains a 10" drive unit built along the same extravagant lines as its big brother i.e. over engineered and dead gorgeous. The internal volume behind this upper bass unit is 14 litres and it works in the range from 100Hz to 400Hz. It also marks the Maidstone's first divergence from conventional practice. A lot of full range speakers step straight from a very large bass driver to a very small midrange unit, which can cause problems with the integration of the units, and the continuity of the bass. KEF have stepped the drivers far more gradually going 15" -10" -6.5". This, and the fact that they all employ the same doping, should produce musically far more coherent results, from the deep bass right up into the low treble. Or so say KEF and it has to be admitted that this is one of the R109's great strengths.
The top enclosure is bolted, via (gold plated) spacers, to the upper bass cabinet which contains a 6.5" Uni-Q driver handling (almost) the rest of the frequency range. The chassis of this unit, like the others, is a high quality die-casting finished to an excellent standard. For those of you who haven't encountered this KEF innovation, the Uni-Q driver demands closer investigation. Their design features a highly developed tweeter situated within the coil assembly of the mid-unit, thus approaching the ideal of a 'single point source' delivering a well behaved dispersion pattern with good phase characteristics off axis - or so we are told.
The overall look of the Maidstone strikes me as something that started out as an ugly functional object, before being tamed to make it more aesthetically acceptable. The 25mm thick (50mm in the bass unit) front baffles are curved in an easy going fashion and veneered in handsome grain matched mahogany whilst the back, top and sides of the cabinets are finished in a satin black. KEF have lavishly adorned the Maidstone's by gold plating virtually all the exposed metal parts. This extravagance is not too much in evidence until you see the back of the units which boast beautifully finished terminal plates and binding posts. There is also what might be mistaken for a nameplate on the top of the mid/HF box. Its true function is to facilitate the addition of a super tweeter, not something commonly encountered in this part of the world except by the RSPCA, but apparently becoming a trend in the far east. One wasn't supplied and I certainly didn't miss it.
The terminal plates are situated on the back and top of the bass cabinet, the former providing input to the crossovers, the latter, output to the mid and top drivers. This adds up to a staggering twenty binding posts per loudspeaker (all gold plated...). With this glut of connections available, various configurations for set-up present themselves. Everything from single wiring (using supplied gold jumpers) through to full 4-way active drive can be accomplished. KEF advocate an approach which lies somewhere in between. They recommend passive bi-amplification, for which, as we'll see, they have good reason.
Below the terminal boards lie the crossovers. One unit serves the two bass sections, the other the mid and high frequencies. Once again, high build quality is evident and KEF's matching of crossover components and drive units is second to none. This usually pays dividends with imaging and presentation of detail. A small amount (± 1 dB) of level adjustment is available for the high frequency energy level, via a screw terminal, to compensate for different acoustic environments (and of course it too is gold plated).
The mid-range cone material is doped polypropylene with a gentle curve whilst the tweeter is a 1" fabric dome, ferrofluid cooled within a neodymium magnet assembly.
One minor reservation about the crossover layout. I might be out of line here, but it seems to me that in a speaker of this quality particularly bearing in mind the unused space behind the top section of the cabinet, that there would be advantages in externally mounting the cross-over? If there is any evidence of electronic components being microphonic (and I firmly believe that there is) surely the last place you would want to situate them is inside a bass cabinet - especially one generating the volume levels of which the Maidstone's are capable.
Finally on the construction front, the bass cabinet is supplied with cones which screw into the bottom plate. The front ones are quite a bit taller than the rear, thus tilting the system back by a few degrees. As one would expect, the Maidstone comes with a full and lavishly presented handbook for installation and operation - yet again typical of the attention to detail throughout the whole system.
In spite of their size, the KEF's are not especially sensitive: 91dB is specified, along with a 4-ohm load. KEF's Conjugate Load Matching is not in evidence here - a lot of their earlier models incorporated circuitry to ease the load on the amplifier and thus make them easier to drive. Ironically I think we can safely say that the Maidstone is something of a power hungry monster, and the preference for bi-amping is understandable.
The system I used with the big KEF's comprised the Meridian 508.24 for CD replay and the Linn for vinyl. These were coupled with the Pass Labs phono stage, Primary line stage and mono blocks, which rose to the occasion admirably. It is rare that I'm able to safely unleash over 300 watts into any loudspeaker but it was clear that the Maidstone's were having a good time with them. Connections were made with Chord Company Chorus and Odyssey which did sterling service. Towards the end of the listening, and feeling the demand to try something a little more exotic (and in keeping with a twelve grand speaker) I prised a set of the ruinously expensive Nordost SPM from the editor's sticky grasp. And yes, it made a big difference, building on the already impressive performance.
The Maidstone's need plenty of space around them which was no problem fore and aft but unfortunately in my room I could not quite give them the clearance they deserved to the sides. They constantly reminded me of the fact, so be warned, you will need a lot of space.
The first thing you notice about the sound of the Maidstone's is the sheer, enormous scale that they present. There is an impact to music that a good large speaker can provide by way of a combination of dynamics, bandwidth and effortlessness that can be totally addictive. The Maidstone's are good. There is a sure footedness to their presentation that instils a confidence not available from lesser designs. To be more specific, the Maidstone puts all the fundamentals in the right place, and at the right time, with such authority that all other aspects of the performance fall into place.
Rhythmically complex music, such as Peter Gabriel's soundtrack to The Last Temptation of Christ is conveyed in a fashion that leaves no doubt as to who is in control. The drummers, all twenty of them! As the music builds up, and each successive layer of percussion is added, there has been a sense of doubt with many systems that they might lose the plot or even their bass units when things start getting frantic. Not so with the Maidstone's. I have never heard a speaker remain so totally in control with this music, even at really frightening levels. They manage to pass it off with a slight sense of arrogance as in "is that the best that you can do?" No problem. There is something about the combination of the two bass units that gives music of this sort both the weight and agility which makes it so exciting. In my experience a single large bass driver cannot successfully deliver both of these qualities. Likewise, large scale orchestral works such as Brahms' Symphony Nos. 3&4' are beautifully reproduced, again with that sensation of immense scale countered with poise, and where called for, drama. It was impossible for me to listen to just one movement, I had to play the whole thing through. By contrast, small scale recordings such as the Shostakovitch string quartets (all of them!) were reproduced with an intimacy that was enthralling, combined with a lush but accurate string tone, built on the resonant presence of the instrumental bodies. Although there was plenty of depth, the Maidstone's found it difficult to define a convincing lateral image of the instruments, resulting in a lack of precision across the soundstage.
Traditionally the Uni-Q drivers have excelled at image definition, to the extent that it wasn't essential to be square in the middle of the loudspeakers. This is where I suspect that the width of the room was upsetting the situation but unfortunately I didn't have the opportunity to try them in a wider one. Besides, moving them would have been a nightmare! I have heard them produce lateral images (although not of the exaggerated, pinpoint variety so fashionable at present), so this will have to remain a 'listen to them in your own room' judgement.
A session which remains highlighted in my memory of these loud-speakers occurred late one night, listening to the Naxos recording of Arvo Part; Fratres. This eerie music has a quiet, pensive beginning which grows to a thunderous dynamic crescendo before dying down again, all within the first movement. It is intensely emotional stuff, and I was left enthralled and not a little scared, particularly as I was in the house alone.
As you will probably gather, I was enjoying myself. I had to force myself to explore some of the other possibilities using ancillary equipment that I had on hand, because every time I went into the room I just wanted to listen to more music. I did get round to bi-amping the Maidstone's with two Naim NAP 250's, and this proved to be a good match, sounding a little tidier and more controlled, although lacking the drama and sense of scale that the Primary valve amps could generate. The attributes of the Naim amplification shone through, with good rhythmic delivery and timing. I began to wonder what four NAP 135's would sound like... but there just wasn't time, and by this stage I felt as if I already had a good feel for the KEF's capabilities.
It was also interesting to observe the reaction of other people, especially those not interested in hi-fi. The normal response to a pair of loudspeakers the size of the Maidstone's is an immediate 'How much do they cost?' closely followed by remarks concerning the justification of such expenditure, prior to a cursory listen. These KEF's elicited somewhat different behaviour. Possibly because of the grand scale with which they reproduced music, the normally casual listener was often seduced into a longer relationship. At one stage whilst the review pair was in residence, what started as an evening barbecue instead became an intensive listening session. I ended up with eight people present (none of them remotely interested in hi-fi), rifling my music collection for requests, and wallowing in the sheer enjoyment of the sound, to the virtual exclusion of conversation. This continued until just after 5 o'clock in the morning!
There is no doubt that the Maidstones are remarkable. Like any esoteric product, they demand skill and patience in setting up, and the choice of suitable amplification is certainly a limited one. Yet again we are confronted with a product that demands the agility and subtlety of a small amplifier combined with the sheer muscle and current drive of a much larger unit. Fortunately because they work so well with bi-amplification, this dichotomy is not the problem it might otherwise be. Similarly they are demanding of the room. These loudspeakers excel at presenting music on a large scale and in order to achieve their full potential they need plenty of space to breathe.
Have KEF met their design objectives? Yes, I believe they have. The Maidstone's did all the things that you would expect a large loudspeaker to do and with supreme confidence. Are they value for money? I just don't know That depends on your particular outlook and circumstances, I know that I spent as much time as I possibly could listening to the Maidstone's, and when the time came for them to go I realised that there was going to be a considerable period of readjustment. I still miss them.
TECHNICAL SPECIFICATIONS
Product Description: 4-way, stacked enclosure loudspeaker.
Drive Units:
Bass: 380mm doped paper cone, double suspension, under hung voice coil.
Bass/Mid: 250mm doped paper cone, underhung voice coil.
Midrange: 160mm doped polypropylene cone.
Tweeter: 25mm ferrofluid cooled, fabric dome.
Cabinets:
Bass: 145 litre, 25mm braced MDF, 50mm baffle. Reflex loaded.
Bass/Mid: 19 litre, 25mm braced MDF.
Mid/Treble: 6.5 litre, 25mm braced MDF.
Crossover Frequencies: 100Hz, 400Hz, 2.8kHz
Frequency Response: 35Hz - 20kHz ± 3dB. -6dB - 30Hz.
Sensitivity: 91dB/w
Maximum SPL: 118dB
Power Handling: 400 watts
Impedance: 4 Ohms
Weight: 87kgs
Dimensions (WxHxD): 600 x 1188 x 671 mm
Finish: Mahogany / Black Satin (Other veneers available to special order.)
Price: £12000
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